1. Field of the Invention
This invention relates to a pipe joint, and more particularly, to one for a pipe having a diameter of 20 mm or less and used in a pipeline for supplying oil or gas to a vehicle or machine.
2. Description of the Prior Art
A known pipe joint of the type to which this invention pertains is shown in FIG. 24, and comprises a pipe P, a connector 1 and a socket 2. The connector 1 has an axial bore 24 and a diametrically enlarged chamber 23 which is axially contiguous to the axial bore 24 and includes a chamber having a small diameter and holding seal rings 26, and a chamber contiguous to it and having a large diameter. The wall of the chamber having a large diameter has a pair of diametrically opposite engaging holes 29 and 29'.
The socket 2 has an annular end wall 55 and a body extending axially from the end wall 55 and including a pair of radially outwardly directed engaging portions 28 and a pair of radially inwardly directed engaging lugs 25. The socket 2 is fitted in the connector 1. The engaging portions 28 of the socket 2 are engaged in the engaging holes 29 and 29', respectively, of the connector 1 to hold the socket 2 in position. The pipe P has a radially outwardly projecting annular wall protrusion P' near one end thereof. The wall protrusion P' is held between the engaging lugs 25 and an annular bush 27 in the connector 1.
The pipe P is easy to fit in the connector 1 and the socket 2 by a single step of operation if it is inserted at one end into the connector 1 until its wall protrusion P' is moved past the lugs 25 by forcing them radially outwardly. Upon movement of the wall protrusion P' past the lugs 25, the lugs 25 move back radially inwardly to their original positions and engage the wall protrusion P' to hold the pipe P against detachment.
When the pipe P is inserted as described above, its wall protrusion P' causes the lugs 25 to make an arcuate motion at their free ends. The arcuate motion of the lugs 25 includes their axial displacement toward the bush 27 and it is, therefore, necessary that the free ends of the lugs 25 and the bush 27 have therebetween a distance which is sufficiently large to permit the axial displacement of the lugs 25, and which is larger than the thickness of the wall protrusion P' of the pipe P. It is, therefore, likely that the pipe P may be displaced axially of the pipe joint, since its wall protrusion P' is not tightly held between the lugs 25 and 27.
It has also been proposed that the relevant portion of the connector 1 and the bush 27 have an inside diameter which is equal to, or slightly smaller than, the outside diameter of the pipe P, so that the pipe P may be tightly fitted so as not to be displaced radially of the pipe joint. This proposal is, however, not practically acceptable for the efficient manufacture of a large number of pipe joints, since the pipe is not easy to fit in the connector or bush having such an inside diameter, but it is usual practice to form the connector and bush with an inside diameter which is slightly larger than the outside diameter of the pipe. Thus, it is likely that the axial and radial displacement of the pipe may occur and cause the seal rings 26 to get worn and fail to maintain a tight fluid seal, particularly when the pipe joint is subjected to vibration.